Mash duration and efficiency

[Tomp]

Does anyone know how mash duration affects efficiency?

Should the ideal mash be an hour or 90 minutes, or does it depend on what you are trying to achieve?

[PeeBee]

It's on a scale of rapidly diminishing returns. If temperature is about right it's probably done in 45 mins (maybe 30), further mashing may (may!) alter the balance of long and short chain sugars (more time resulting in more short chain). But an hour to 90mins does the job. Not a lot happens after that (ask the all-night mashers brigade). Temperature has a more striking effect, hot (69C) for more complex sugars (that may produce more striking flavour) and cool (62C) for more fermentable sugars.

[Eric]

Does anyone know how mash duration affects efficiency?

Should the ideal mash be an hour or 90 minutes, or does it depend on what you are trying to achieve?

If it's within the accepted range for temperature and pH, there will be no change in efficiency after maybe 20 minutes, in some cases less. From that point on all starch will be sugars, just that they will be in the wrong proportion for the most favoured beers. So yes, time has most effect on what you are trying to achieve.

In a brewery near to here they always mashes for 60 minutes, the brewer is convinced it makes better beer than when mashed for 90 minutes. He makes excellent beers, just that they all taste very much alike.

I mainly mash for between 75 and 90 minutes, but can go to 2 hours. Generally a starch test after 30 minutes confirms full conversion. For highest efficiency it is the sparge that is critical.

[chris2012]

That's very interesting Eric do you mean that despite the starch conversion being done in say 20 mins, something important continues happening long after that. Do you know what that is?

[Eric]

That's very interesting Eric do you mean that despite the starch conversion being done in say 20 mins, something important continues happening long after that. Do you know what that is?

A little bit, there is so much that happens from starch end point until the enzymes are totaly denatured that I think I'll be long gone if there's ever agreement of what form they take and what influence they have.

Put simply (the little I know) starch is first converted to long chain unfermentable sugars. Once these complex sugars are produced, other enzymes convert those into shorter chain sugars. There's a masive amount of research on this but is very wide ranging and detailed as the actions are influenced by just about every variable such as temperature, enzyme health, mash thickness, grains incorporated, minerals in liquor, pH, time, and the rate of change in any of these and others as the process proceeds under these changing conditions. In other words, virtually everything changes.

A little example of how interconnected the process is. This was written about 100 years after the first scientific investigation into the subject.....

The total beta amylase activity would be sufficient for a normal mash but more susceptible to inactivation by high temperatures. The difference was most marked between 80°C and 85°C when beta amylase was rapidly inactivated but alpha amylase retained considerable activity. The predicted effect of raising the mashing temperature would be a shift in wort composition away from the products of beta amylase (i.e. a mixture of fermentable and non-fermentable sugars). Figure 3 shows that there was very little difference in the amount of extract obtained when mashing over the range of temperatures 70°C to 85°C. The sugar spectrum, however, changed considerably, giving lower fermentabilities at higher temperatures. Furthermore, decreasing mash thickness also reduced the wort fermentability. It is known that dilution of enzyme systems increases enzyme instability, but, as with temperature, beta amylase was more susceptible to dilution than alpha amylase.

The activity of mash enzymes is more susceptible to heat in a thin solution than in a mash as shown in Figure 5. Even at 80°C very little alpha amylase survived beyond 10 minutes. Nevertheless, this would be sufficient time for the enzyme to remove any remaining starch. The beta amylase would be so rapidly inactivated that it would have no effect on fermentability. As may be expected from the fermentability data, the wort starch content increases with inactivation of the enzymes. The biggest changes were seen at 85°C perhaps because at other temperatures alpha amylase activity compensated for loss of beta amylase. This would also explain why the increase in wort starch was considerably less than the decrease in wort fermentability for the same temperature change. Between 65°C and 80°C any loss of beta amylase would be compensated for by alpha amylase attack on the remaining starch. However, at 85°C the alpha amylase is also unstable so that changes in mash thickness have a greater effect on wort starch.

[PeeBee]

Eric is braver than me, the "all night masher" brigade have teeth and I've already been chewed up once.

But the posts highlight a particular fact, the enzymes don't not denature at 65C, they denature at a slow enough rate for the job to be all done. Just like temperatures of 70-75C don't halt conversion instantly. Historical brewing made use of high temperatures ... apparently. But high temperatures are risky, and commercially sticking to 63-66C was the best way to greatest extract. But I also hear high temperatures (69C+) generate the best flavours but may result in lower extracts. So as home-brewers can't we mess with parameters rather than be dictated to by economic concerns?

That doesn't help "Tomp"!

[Eric]

Eric is braver than me, the "all night masher" brigade have teeth and I've already been chewed up once.

But the posts highlight a particular fact, the enzymes don't not denature at 65C, they denature at a slow enough rate for the job to be all done. Just like temperatures of 70-75C don't halt conversion instantly. Historical brewing made use of high temperatures ... apparently. But high temperatures are risky, and commercially sticking to 63-66C was the best way to greatest extract. But I also hear high temperatures (69C+) generate the best flavours but may result in lower extracts. So as home-brewers can't we mess with parameters rather than be dictated to by economic concerns?

That doesn't help "Tomp"!

Most flavours from any given grist are provided by yeast activity. Of course the resut depends upon what they might be fed.

As for mash temperature, it is supposed that before the days of a thermometer it was difficult to judge if the mash was right. When you next mash in and have the temerature set, stick your hand into the grains almost to your wrist and start counting. I bet you don't get more than halfway to ten before you pull it out, yet find you have not been burned or scalded. If you were scalded or found no difficulty, there's an even chance your thermometer is wrong.

If you mash all night, life must be rough.

[Sadfield]

Eric, do you have a link to the document you referenced, please. I'm building a recipe for doing a 0.5% beer, I'm looking to reduce fermentability as much as possible, so any tricks and tips would be helpful. I've already factored in high mash temp, thicker mash and the possibility of reducing fermentability using pH adjustment.

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[Eric]

It was in a paper titled "THE EFFECTS OF MASHING TEMPERATURE AND MASH THICKNESS ON WORT CARBOHYDRATE COMPOSITION" presented to the IoB in 1990 and read the following year.
Sorry, can't give you a link, but will give you the piece you wish, it's quite concise.

Temperature and mash thickness are shown to affect both mash performance and enzyme activity. Alpha amylase was found to be considerably more resistant to heat inactivation than was beta amylase. This difference was reflected by changes in wort fermentability that were manifest at temperatures below those which affected levels of extract. Increasing the mashing temperature from 65°C to 80°C had only a slight effect on extract but reduced wort fermentability from over 70% to less than 30%. At 85°C and over, when temperature had a significant effect on alpha amylase, as well as on beta-amylase, extract was lost and starch was present in the wort. Diluting the mash with liquor had a similar effect to that of increasing temperature on both the amylolytic enzymes and on the mash performance. Thin mashes contained more starch and fewer fermentable sugars than did thick mashes at the same temperature. These changes can be related to the stability of the amylolytic enzymes.

So basically you are looking for a full volume, 10 minute mash at 80C or a touch above with minimal calcium present to protect beta amylase and very low alkalinity to get pH 5.6. Even then you might at best get fermentability down to 25%, so it would only be practical for what would in more normal conditions be a 1.5% beer. You could of course include malts that give more residual sweeness, but I'm not sure you would be pleased with the result. Yeast can also play a big part, a lesser attenuating one would only be a starting point as it may be necessary to stop it by pasteurisation.

[Jocky]

For grists with a decent amount of modern malted barley then I've not seen improvement in efficiency past 45 minutes.

I mash high wheat grists (50%+) a bit longer - 90 minutes - as I've had poor efficiency in shorter mashes and also I like to spend a good amount of time recirculating wort to filter out the additional flour and fine particles that wheat tends to produce.

I recently brewed a saison that was well received and that was mashed for 2.5 hours - although that was more out of necessity due to having to go out. I wasn't too worried as I wanted to make the wort as fermentable as possible as I wanted a really dry beer. It worked - it went from 1.058 to 1.003.

[chris2012]

Jocky - that's very interesting about '1.058 to 1.003', do you recall what temp you mashed at? I'm assuming close to 65C?

Eric - thanks for your reply, I'm going to take my time to go through that properly in a bit!

[PeeBee]

It was in a paper titled "THE EFFECTS OF MASHING TEMPERATURE AND MASH THICKNESS ON WORT CARBOHYDRATE COMPOSITION" presented to the IoB in 1990 and read the following year.
Sorry, can't give you a link, but will give you the piece you wish, it's quite concise.

...

http://onlinelibrary.wiley.com/doi/10.1 ... 055.x/epdf

Nice one Eric. Google is a wonderful tool isn't it.

[Sadfield]

Thanks Eric.

I think my approach is going to be a sum of many parts so that one doesn't dominate.

When brewing Nanny State, Brewdog use a grist of Malted Rye and crystal malts, mashed at 65C and ferment with American yeast. I don't much care for the result, but a percentage of this grist may work, combined with a hotter, thicker mash and use of a less attenuative yeast that finishes sweeter, WLP028 Edinburgh Ale bring my preference.

The is also anecdotal evidence that mashing with lactic acid to lower than 5.2 reduces attenuation, with little effect on flavour, as the beer hits terminal pH before full attenuation. Which may be another weapon in the armory.

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[Jocky]

Jocky - that's very interesting about '1.058 to 1.003', do you recall what temp you mashed at? I'm assuming close to 65C?

Eric - thanks for your reply, I'm going to take my time to go through that properly in a bit!

It was 62/63c. Note that I was using WLP565 which is a saison yeast that has high attenuation given the right wort and circumstances.

A couple of weeks ago I also did a lager that was mashed at 62c for 15 minutes and then 66c for 45 minutes specifically to help dry it out, and it has gone from 1.054 to 1.008. A previous version with a single infusion around 66c for an hour finished at 1.013 and was too sweet. Both used WLP833.

[PhilB]

Hi Tomp
At the risk of being labelled as one of the ' "all night masher" brigade ', when I have mashed overnight I have experienced a small increase in (brewhouse) efficiency ... I couldn't possibly say whether that's due to continued alpha-amylase activity or simply due to the extended soaking helping in the extraction of the sugars to a more "accessible" state (because as Eric says above "For highest efficiency it is the sparge that is critical.") but it does seem to "win" me a percent or two over a "normal" mash ... of course, that's not why I do an overnight mash (nor is it because "life is rough" ), it just suits better sometimes

Hi Sadfield
Have you considered "in bottle pasteurisation" as an approach for your low ABV beer ... ISTR reading that that's the preferred approach for home brewers to make Malzbier

Cheers, PhilB